A switch is a component utilized to reversibly open and close a circuit. A switch may be considered to have two operational states, with one of the states being an “on” state and the other being an “off” state. Current flow through the switch will be higher in the “on” state than in the “off” state, and some switches may permit essentially no current flow in the “off” state. Switches may be utilized anywhere in an integrated circuit where it is desired to reversibly open and close a portion of the circuit.
A type of circuitry that may be present in an integrated circuit is memory. The memory is used in computer systems for storing data. The memory cells are configured to retain or store information in at least two different selectable states. In a binary system, the states are considered as either a “0” or a “1”. In other systems, at least some individual memory cells may be configured to store more than two levels or states of information. The different memory states of a memory cell may correspond to different electrical properties within the cell, and may, for example, correspond to different resistances through the cell. For instance, one of the memory states of a binary system may be a high-resistance state of the memory cell, and the other of the memory states of the system may be a low-resistance state of the cell. Accordingly, reading of the cell may comprise determining current flow through the cell under a pre-defined voltage.
One type of memory cell is a so-called cross-point memory cell, which comprises programmable material between two electrically conductive electrodes. Numerous programmable materials are known which can be suitable for utilization in cross-point memory. For instance, phase change materials (such as, for example, various chalcogenides) may be utilized as programmable materials. Memory that utilizes phase change material as the programmable material is sometimes referred to as phase change random access memory (PCRAM). As another example, some programmable materials may utilize ions as mobile charge carriers to transition from one memory state to another. Such programmable materials may be incorporated into Resistive Random Access Memory (RRAM).
A difficulty in utilizing cross-point memory is that there can be substantial leakage of current through the cross-point memory cells, and such may adversely lead to errors during retrieval of stored data from a memory device. Accordingly, diodes or other select devices are commonly paired with the memory cells to assist in control of current through the memory cells. A switch can be a suitable select device.